The present invention relates to the measurement of fans in industrial applications with various industrial processes. In my prior U.S. Pat. No. 5,050,092, incorporated herein by reference, I disclosed a method and apparatus by which the fan efficiency of such fans can be measured in a non-invasive manner, which did not require direct interaction with the fan. It is also useful to know the flow rate through such fans to determine the quantity of gas and gas carried matter through the system. Direct gas velocity measurements are difficult to monitor in a dirty flue gas duct system, because velocity sensors are prone to plug, corrode, and generally deteriorate as a result of the continuous exposure to flue gas, however, temperature and pressure readings can be obtained with reliability in such a system.
There exists a need for a simple unit capable of measuring the parameters selected to determine flow rate on a substantially instantaneous and incremental basis to determine flow rate without affecting fan performance.